Prior co-owned patents dealing with locks for Whisler type adapters include U.S. Pat. Nos. 4,267,653 and 4,271,615. Earlier patents dealing with the same subject matter include U.S. Pat. Nos. 3,572,785 and 3,722,932.
The market today is almost totally breakdown maintenance-oriented rather than preventive maintenance-oriented for the simple reason of the economy in money and available staff. Job conditions are as tough as they have ever been and machine power is still at its highest, so the loading on the system is extreme. The Whisler lip system has already been a stellar performer as long as the critical bearing areas were maintained so that the adapter fits tight on the lip. This is no longer the case for the above mentioned reasons and had led to high frequency of adapter leg failures and/or the loss of the C-clamp and wedge sysytem It is almost impossible to predict what happens first, i.e., does the wedge become ejected, then the C-clamp falls out, thereby exposing the adapter leg to a loss of support and failure or total loss without failure, or does the adapter leg fail and then the lock sytem eject as a secondary action? We are certain that wedges do eject and C-clamps are lost, even though the two are welded to each other, so this can be considered a primary factor in the failure and/or subsequent loss of the adapters.
In our opinion, this occurs because of the looseness in the fit between the adapter and the lip. The primary bearing at the forward edge of the lip where it bears in the adapter crotch, with secondary bearing importance existing in the back of the legs, where bearing is required for a proper C-Clamp and wedge assembly to operate properly.
We have overcome this problem by allowing the entire adapter system to move under high stress static or shock loads rather than just the areas forward of the C-clamp and wedge in the case of the conventional wedge type connection. This allows for more balanced stress distribution, hence producing a stronger overall assembly. Additionally, the system is easy to install and remove, as opposed to existing wedge type of arrangements, thereby enhancing the customer service advantage and safety as well. Finally, the lock system overcomes the vertical forces that always exist in any wedge type C-clamp and wedge system that are always tending to eject the wedge from assembly. More particularly, the invention makes use of a C-clamp member and a wedge member with spring means interposed between the two members and constituting the only bearing contact between the two members when the adapter is not under load.
Where the wedge is in assembly with the C-clamp, this combination in assembly with the back of the Whisler adapter legs is in a totaly constrained, nearly non-deflectable capacity. This puts considerable extra loading on the legs of the adapter forward of the wedge, as the adapter moves in line with the description above.
Based on our theory on adapter movement on the lip, we conceived an improved design Whisler-style adapter system that is intended to live under the environment of a loose fitting system due to wear and tear of the bearing areas, because this appears to be the case more than 90% of the time these days.
Springs in the past have not been widely used as locking devices in excavating teeth. Illustrative of what has been done is U.S. Pat. No. 3,832,077, which shows a spring in connection with a locking pin for securing the point to the adapter. Although the adapter illustrated is of the Whisler type, it does not use a C-clamp and wedge but rather is intended to be secured to the lip by means of bolts. Bolts have long been avoided for securing adapters to lips of excavating equipment because of the difficulty of disassembly--the threads becoming worn or filling with compacted material.